This invention relates to conveyors, and more particularly, to a belt conveyor capable of accumulation.
Conveyors of the wheel and roller-type utilize a variety of accumulation devices, a more popular type being the kind where the application or release of propelling force on the wheels or rollers is effected through changes in the vertical position of the propelling member. One way of effecting this is by supporting the belt on flattened rollers. Another way of doing this is by supporting the belt on pivoted hangers. Examples of these types of accumulating conveyors are illustrated in U.S. Pat. No. 3,253,697 entitled VARIABLE PRESSURE CONVEYOR issued May 31, 1966 to Maynard J. DeGood and Clyde L. Bowman, U.S. Pat. No. 3,062,359 entitled ACCUMULATOR CONVEYOR issued Nov. 6, 1962 to T. C. McGow, et al., and U.S. Pat. No. 3,012,652 entitled LIVE ROLLER CONVEYOR WITH SENSING issued Dec. 12, 1961 to N. C. Poel, et al. These types of conveyors provide both selective accumulation and automatic termination of article movement when the lead article's forward motion is stopped for any reason.
A principal drawback with roller and wheel conveyors is that the article containers themselves must be of sufficient strength to support the articles contained therein since the roller or wheel support is intermittent in the sense that it does not provide a continuous support surface. Thus, if the container has an insufficient bottom area to provide adequate support for its contents or it is deteriorated for example by moisture, the bottom of the container interferes with proper movement along the conveyor. There are many types of articles and containers which cannot be effectively transported on roller or wheel conveyors, such as for example, chimed drums, crated goods, or bagged articles such as potatoes, citrus fruit and the like. Further, no practical sensing mechanisms are available to detect such articles or containers.
Present ecological trends in this country indicate a dissatisfaction with the size and material consumption of individual packaging as presently practiced. Such packaging provides a vast amount of waste which must be handled and disposed of. An alternative trend is foreseen whereby goods will be packed and shipped in much less massive, or, by present standards, flimsy or low strength packages. Where relatively flimsy packages are utilized, a belt conveyor offers distinct advantages over a wheel or a roller conveyor since it provides a substantially continuous support surface. Satisfactory accumulation for belt conveyors, however, has not been obtained. Still another drawback to the present accumulation art is that regardless of the type of conveyor, the devices of the prior art are quite expensive and complex since they require, in some fashion, a complete shifting of a major component part of the drive support undercarriage. Thus, there is a need today in this art for an improved mechanism for providing conveyor accumulation at selected desired locations--particularly one that operates satisfactorily in a belt conveyor.